第三相流体对两相驱替行为影响的孔隙尺度研究

Multiphase displacement behavior in capillary and porous media is a typical flow phenomenon widely encountered in enhanced oil recovery and prevention and control of groundwater pollution. To explore the influence of an immiscible third-phase fluid on the two-phase displacement behavior，a threephase lattice Boltzmann color-gradient model is applied for the pore-scale investigation of the displacement pattern and efficiency in both a single capillary and a porous medium. Results show that in a single capillary， the displacement efficiency first increases and then decreases with increasing the amount of the thirdphase fluid. Introducing an appropriate amount of the third-phase fluid enhances the stability of the displacement front and thus promotes the transition from fingering displacement to stable displacement. The stabilizing effect of the third-phase fluid is strengthened by either increasing the viscosity ratio of the injected fluid to the third-phase fluid or decreasing the capillary number. In a porous medium，the influences of the third-phase fluid amount and the capillary number show good agreement with those observed in a single capillary. Specifically，the displacement efficiency exhibits a first increasing and then decreasing variation with the increase in the amount of the third-phase fluid，while it monotonically decreases with the increase in the capillary number. This study not only enhances the understanding of introducing a third-phase fluid to regulate the two-phase displacement behavior，but also provides theoretical reference for optimizing industrial applications related to multiphase displacement，such as the extraction methods of crude oil.